1. Field of the Invention
This invention was made with Government support under Contract No. DAAE07-00-C-N086 awarded by the United States Army. The Government has certain rights in this invention.
2. Description of the Related Art
Gas turbine engines are frequently required to direct burn flow to various manifolds containing fuel nozzles and to purge residual fuel from these manifolds when they are not flowing fuel. In one known system, fuel flow to a start manifold is stopped after starting the engine by closing one solenoid to block metered fuel flow to the starter manifold and opening a second downstream solenoid leading to a holding tank. Pressure in the combustion chamber then backflows dirty combustion gases from the combustion chamber through the nozzles and to the holding tank. It is desirable to avoid the flow of dirty combustion gases through the start manifold and to eliminate the weight and bulk of a holding tank.
In another known system illustrated by U.S. Pat. No. 4,041,695, purging of both primary and secondary manifolds at engine cessation is achieved using a fuel flow solenoid and an air flow solenoid which operate inverse to one another, that is one is closed while the other is open and visa versa. Clean engine compressor air from an accumulator and filter purge both primary and secondary manifolds at the same time, but only upon engine cessation. This patent also teaches the use of a plurality of valves that open and close based on pressure drops to achieve fuel flow division between the primary and secondary manifolds. It is desirable to achieve manifold purging at times other than only at engine cessation. The capability to purge a particular manifold without purging other manifolds at the same time is also desirable.